Permanent magnet synchronous motors (PMSMs) are used in a wide variety of applications. FIG. 1 is a simplified diagram of an example PMSM 100. PMSMs typically comprise a rotor 108 configured to rotate within a stator 102. Permanent magnets 106 are mounted on or buried within the rotor 108 (PMSMs with permanent magnets that are buried within the rotor are referred to as interior permanent magnet, or IPM, motors). The stator 102 includes a number of electrical windings 104 arranged to surround the rotor 108. During operation, electrical current through the windings 104 sets up a magnetic field within the air gap 110 between the rotor 108 and the stator 102, and the interaction between the magnets 106 and the magnetic field causes the rotor 108 to rotate, producing torque. The speed and direction of the rotor 108 can be controlled by controlling the current through the stator windings 104.
PMSMs are often controlled using field oriented control (FOC) techniques. However, since sensorless PMSMs lack directly measured load information, smooth transition from the stopped state to closed-loop sensorless FOC control of a PMSM can be difficult. This is because, lacking information regarding the load on the PMSM, the FOC control system may be designed to apply an excessive amount of torque during the transition to ensure that the motor achieves a minimum amount of speed to generate usable back-electromagnetic force (back-EMF) information. This excessive torque can cause the motor to over-speed or stall.
The above-described is merely intended to provide an overview of some of the challenges facing conventional motion control systems. Other challenges with conventional systems and contrasting benefits of the various non-limiting embodiments described herein may become further apparent upon review of the following description.